The overall focus of our laboratory is on the function of the 70 kDa heat shock proteins in both normal cellular processes and in the heat shock phenomenon. Although we ultimately plan to investigate the function of these proteins in yeast, we are approaching this question by investigating the relationship of the heat shock proteins to a homologous protein, the uncoating ATPase which appears to be involved in endocytosis in mammalian cells. This protein strips clathrin from clathrin coated vesicles in a process which requires ATP. Our laboratory has isolated coated vesicles, clathrin, clathrin-derived baskets, and the uncoating ATPase from bovine brain. We have developed an assay to quantitatively measure the extent to which the uncoating ATPase removes clathrin from both coated vesicles and clathrin baskets. In contrast to other researchers who have reported that the uncoating ATPase catalytically removes clathrin from these structures, our preliminary results indicate that it may act stoichiometrically. We are currently investigating whether this is indeed the case, and if so, how this stoichiometric effect relates to the ATPase activity of the protein.